The present invention relates to a sealing assembly for relatively rotating mechanical members.
As is known, in normally used sealing assemblies, a substantially annular sealing member is interposed between a first and a second shield, which are fitted respectively to a first and a second member in relative rotation, e.g. a shaft and respective seat.
The sealing member, which is carried integrally by a first of the shields, has one or more sealing lips, which cooperate in sliding manner with respective portions of a second of the shields, with respect to which the sealing member is movable. Obviously, choosing the right material for the sealing member is vitally important, by possibly affecting performance of the sealing assembly as a whole.
Highly elastic elastomeric materials are normally used, or preferably PTFE, which, compared with elastomeric materials, has numerous advantages: better high-temperature, oil, and wear resistance; and a lower friction coefficient.
On the other hand, use of PTFE is limited on account of its plastic behavior, i.e. its tendency to deform permanently. In the case of conventional sealing assemblies, in particular, radial-lipped PTFE sealing members may pose problems, especially in the presence of static eccentricity of the shaft-seat connection, or dynamic eccentricity of the shaft. In which cases, in fact, the poor elasticity of PTFE prevents adequate absorption by the sealing member of the undesired movement caused by such eccentricity, thus impairing operation of the sealing assembly as a whole.
It is an object of the present invention to provide a sealing assembly designed to eliminate the aforementioned drawbacks, and which at the same time is cheap and easy to produce.
According to the present invention, there is provided a sealing assembly for relatively rotating mechanical members, comprising a first and a second shield member fitted respectively to a first and a second of said relatively rotating members; and a low-friction-coefficient sealing member having a sealing portion cooperating with said first shield member, and a root portion carried integrally by said second shield member; characterized in that said sealing member also comprises a connecting portion shaped to define a hinge region between said root portion and said sealing portion.
In other words, the connecting portion forming a hinge between the root portion and the sealing portion provides for increasing the flexibility of the sealing member. This is particularly advantageous when the sealing member is made of PTFE, by enabling exploitation of the properties of PTFE (low friction coefficient, good wear, high-temperature, and oil resistance) while at the same time enhancing the elastic performance of the sealing member.
According to a further aspect of the invention, said sealing portion defines an axial sealing lip cooperating with an annular projection of said first shield member.
As such, the sealing assembly provides for effectively absorbing any undesired movement caused by mechanical defects, such as eccentricity of the shaft or shaft-seat connection.
According to the invention, the sealing assembly also comprises a toroidal spring housed about said sealing member, between said sealing portion and a first conical portion of said second shield member, which form a V-shaped groove; said spring pushing said sealing portion against said annular projection of said first shield member.
The toroidal spring advantageously provides, on the one hand, for loading the sealing member to achieve a given sealing pressure, and, on the other, for improving the elastic performance of the sealing member and preventing accidental detachment of the sealing portion from the annular projection as a result of any relative axial movement (possible in the presence of slack) between the first and second shield member.